path: root/Documentation
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authorJohannes Berg <johannes.berg@intel.com>2010-11-11 14:05:21 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-11-12 07:55:32 -0800
commit5ada28bf76752e33dce3d807bf0dfbe6d1b943ad (patch)
tree03ce703dce3c5f5afad16a81556608700849d6c5 /Documentation
parent52ca0e84b05595cf74f1ff772b3f9807256b1b27 (diff)
led-class: always implement blinking
Currently, blinking LEDs can be awkward because it is not guaranteed that all LEDs implement blinking. The trigger that wants it to blink then needs to implement its own timer solution. Rather than require that, add led_blink_set() API that triggers can use. This function will attempt to use hw blinking, but if that fails implements a timer for it. To stop blinking again, brightness_set() also needs to be wrapped into API that will stop the software blink. As a result of this, the timer trigger becomes a very trivial one, and hopefully we can finally see triggers using blinking as well because it's always easy to use. Signed-off-by: Johannes Berg <johannes.berg@intel.com> Acked-by: Richard Purdie <rpurdie@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 12 insertions, 9 deletions
diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt
index 8fd5ca2ae32..58b266bd184 100644
--- a/Documentation/leds-class.txt
+++ b/Documentation/leds-class.txt
@@ -60,15 +60,18 @@ Hardware accelerated blink of LEDs
Some LEDs can be programmed to blink without any CPU interaction. To
support this feature, a LED driver can optionally implement the
-blink_set() function (see <linux/leds.h>). If implemented, triggers can
-attempt to use it before falling back to software timers. The blink_set()
-function should return 0 if the blink setting is supported, or -EINVAL
-otherwise, which means that LED blinking will be handled by software.
-The blink_set() function should choose a user friendly blinking
-value if it is called with *delay_on==0 && *delay_off==0 parameters. In
-this case the driver should give back the chosen value through delay_on
-and delay_off parameters to the leds subsystem.
+blink_set() function (see <linux/leds.h>). To set an LED to blinking,
+however, it is better to use use the API function led_blink_set(),
+as it will check and implement software fallback if necessary.
+To turn off blinking again, use the API function led_brightness_set()
+as that will not just set the LED brightness but also stop any software
+timers that may have been required for blinking.
+The blink_set() function should choose a user friendly blinking value
+if it is called with *delay_on==0 && *delay_off==0 parameters. In this
+case the driver should give back the chosen value through delay_on and
+delay_off parameters to the leds subsystem.
Setting the brightness to zero with brightness_set() callback function
should completely turn off the LED and cancel the previously programmed